This proposal on "Electrical Control of Sperm-Egg Fusion" involves an investigation of three questions: 1. How does fertilization cause the egg's membrane potential to change? 2. How does the egg's membrane potential regulate sperm-egg fusion? 3. Does the sperm's membrane participate in regulation of sperm-egg fusion? The methodology involves electrophysiological techniques for intracellular microelectrode and patch electrode recording. 1) We will analyze the conductance increase that occurs at fertilization in the frog egg, measuring the whole cell and single-channel currents, and examining the roles of membrane addition and removal and of calcium in regulating the conductance. 2) We will use cross-species fertilization to determine whether the sperm or the egg contributes the potential-sensitive component involved in sperm-egg fusion. We will begin a project to examine the mechanism of voltage-sensitive fusion by developing procedures for isolating the fusogenic region of the sperm and fusing it with eggs. 3) We will measure the membrane potential at various positions on the guinea pig sperm, and then modify the potential while examining the effects on events leading to sperm-egg fusion. The long-term objectives are to contribute to our understanding of the regulation of sperm-egg fusion and to our general knowledge of fertilization.